Currently, when a gear pump is unified and then the pump body is secured to a housing (casing) accordingly, since a variation may occur in an axial force in case that the axial force is generated to fill a gap between members by screw-fastening, a leaf spring is placed at a base position or a distal end of the pump body, thereby suppressing the variation in the axial force. However, since an arrangement space of the leaf spring is needed and so on, it is not sufficient for miniaturization of the pump device.
Accordingly, in JP-A-2012-52455, it has been disclosed a structure that discharge chambers are arranged at both outer sides of the pump body in an axial direction and members are pressurized each other by a discharge pressure of the pump itself, thereby preventing the gap from being created between the members, so that the miniaturization thereof may be aimed by the elimination of the leaf spring.